The objectives of the applicant's proposed research, which build on her work and accomplishments during fellowship, are: l. To develop and apply a model of in vitro drug metabolism by human and animal liver microsomal preparations to identify specific cytochrome subfamilies mediating biotransformation of a number of psychotropic drugs, and to identify potential inhibitors of metabolism; 2. Using index or probe reactions identified as being mediated by specific cytochrome subfamilies, together with immunochemical and molecular genetic methods, to assess the effects of age and gender on activity and quantity of specific cytochromes; 3. To assess the influence of age and gender on the susceptibility to metabolic inhibition by chemical inhibitors.